Plasma-modified polymer surfaces

Controlling of Stem Cell Behavior on Non-Thermal Plasma Modified Polymer Surfaces... 

The surface contamination will react with the plasma in the same way that the polymer will. That is, if the plasma treatment is not of sufficient duration to remove the contamination, the contaminant will become wettable and will have a modified ESCA pattern similar to that of the polymer. However, it will still be a plasma-treated contaminant layer, not a plasma-modified polymer surface. At normal power levels it is necessary to clean most polymers for several minutes. A treatment of a few seconds... 

There are many different methods for modifying polymer surfaces to improve their adhesion and wetting properties. They include chemical etching and oxidation, ion bombardment, plasma treatments, flame treatment, mechanical abrasion and corona-discharge treatments (1.2). Especially flame and corona treatments are widely used for the modification of polyolefin surfaces to enhance, for instance, their printabilify. Despite the widespread use of such processes in industry, the understanding of the fundamental processes which occur at the polymer surface is very limited. This is undoubtedly due to the shallow depth to which the polymer is modified, typically 5 nm or less. 

A surface analysis technique that has the potential to detect structural chemical changes in polymer surfaces, including low-molecular weight material formation, is static SIMS. Its capabilities for characterizing polymers by virtue of their fingerprint spectrum nave been amply demonstrated in recent years (5 6). The technique is more surface sensitive than XPS and can detect structural differences, even in hydrocarbons (7). It is, therefore, highly complementary to XPS. Nevertheless, only very few applications to the study of modified polymer surfaces have been published. Among these are reports on SIMS analysis of flame-treated polypropylene and plasma-fluorinated polyolefin surfaces (8 9). 

In this paper some applications of static SIMS to a variety of modified polymer surfaces are described. They include plasma treatments in reactive and inert gases, corona treatment in air, as well as thermal and ion beam modifications of polymer-metal interfaces. The examples presented and discussed here primarily serve to illustrate the capabilities of static SIMS for the study of such surfaces and interfaces. More detailed discussions of the actual chemical processes that proceed in several of the systems cited will be published elsewhere. 

The results presented here demonstrate that static SIMS has unique capabilities for the characterization of the surfaces of polymers that have been modified by metal deposition or by plasma or corona techniques. Especially, the introduction of unsaturation and crosslinking are aspects that in some polymers can be observed directly. The formation of low-molecular oxidized material that can be inferred from XPS studies, can also be observed directly. A limitation of the quadrupole-type instrument, which is still the most widely used, is its limited mass range and mass resolution. It can be expected that a considerably more detailed description of modified polymer surfaces can be obtained by application of the more powerful reflectron-type Time-of-Flight SIMS spectrometers, but such studies have, to date, not yet been published. 

Explicitly developed are models of several theoretical multiphase distributions, with corresponding depth-profile results on thin-film plasma polymers, phase-separated block copolymers, and chemical reactions on fiber surfaces. Ion impact is treated from three points of view as an analytical fingerprint tool for polymer surface analysis via secondary ion mass spectroscopy, by forming unique thin films by introducing monomers into the plasma, and as a technique to modify polymer surface chemistry. 

Exposing a polymer surface to various kinds of plasmas can modify polymer surfaces. Plasmas of argon, oxygen, hydrogen, and air are frequently used in plasma surface modification of polymers. Plasmas of non-polymer-forming gases are used in... 

In the case of a polymer surface treated to make it hydrophilic, the value of js is significantly large, and its reduction by virtue of surface configuration change is generally observed. A plasma-modified hydrophilic surface often loses its gained hydrophilicity in a week to 2 months depending on the nature of substrate polymer and of the treatment. 

The (TMS 02) plasma-modified polymers were made considerably more hydrophilic with average cos 0D,a,i= 0.654 (Op,a,i =49.2 11.7) but remain in the domain of amphoteric surface, under the conditions of plasma polymerization used. (TMS + O2) plasma-deposited films were slightly more dependent on the nature of the conventional polymer substrates. This is probably due to the fact that substrate polymers have different oxygen plasma susceptibilities. 

Theoretical and experimental treatments of plasma chemistry processes on polymers have been concisely described. Main phasis has been on properties of the obtained films and modified polymer surfaces and especially on their use in practice. In the future further applications are expected when better understanding of the plasma volume and surface p-ocesses is reached. This may allow to tailor respective films or surfaces according to the need of the particular application. 

Hook, TJ., Gardella, J.A. and Salvati, L, Multitechnique Surface Spectroscopic Studies of Plasma-Modified Polymers II H20/Ar Plasma Modified Polymethylmethacrylate/Polymethacrylicacid Copolymers , J. Mater. Res., 2(1), 132-142 (1987)... 

Over the years, several methods have been developed in order to modify polymer surfaces for improved adhesion, wettability, printability, dye uptake, etc. These methods include mechanical and wet chemical treatments, and exposure to gas phase processes like corona discharge, flame, UV/ozone, glow discharge plasmas, and particle beams. 

Poljraer surfaces can be easily modified with microwave or radio-frequency-energized glow discharge techniques. The polymer surface cross-links or oxidizes, depending on the nature of the plasma atmosphere. Oxidizing (oxygen) and nonoxidizing (helium) plasmas can have a wide variety of effects on polymer surface wettability characteristics (92). 

Other topics recently studied by XPS include the effects of thermal treatment on the morphology and adhesion of the interface between Au and the polymer trimethylcy-clohexane-polycarbonate [2.72] the composition of the surfaces and interfaces of plasma-modified Cu-PTFE and Au-PTFE, and the surface structure and the improvement of adhesion [2.73] the influence of excimer laser irradiation of the polymer on the adhesion of metallic overlayers [2.74] and the behavior of the Co-rich binder phase of WC-Co hard metal and diamond deposition on it [2.75]. 

Gaboury, S. R. Urban, M. W. Analysis of Gas-Plasma-Modified Poly(Dimethylsiloxane) Elastomer Surfaces. Attenuated-Total-Reflectance-Fourier Transform Infrared Spectroscopy. In Structure-Property Relations in Polymers Urban, M. W., Graver, C. D., Eds. Advances in Chemistry Series 236 American Chemical Society Washington, DC, 1993 pp 777-790. 

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